For Your Eyes Only

Overcoming Your Anxiety of Refractive Surgery

A few of your friends have raved about their new and improved vision from their recent Orlando LASIK treatment at Magruder Laser Vision. You, however, have remained a little doubtful about this procedure, which is completely normal. In order to overcome your fear of the unknown, it’s time to learn the facts about this safe and fast procedure. Here are some frequently asked questions:

Will I be awake during the procedure?

Yes. Your eye will be dilated and your eyelids will be held open throughout the procedure. However, there will be a short period of time during the procedure in which the eye cannot see. This period lasts for about 10 seconds. When vision returns, your vision will be vastly improved.

How much pain will I be in?

A mild sedative and numbing drops will be put in the eyes before the procedure to alleviate any pain at the time of the treatment. Pressure may be evident, but minimal to no painful sensations.

Does the laser hurt my vision in any way?

The laser is in contact with the surface of the eye for approximately 10-15 seconds, which causes no damage.

What if I blink or move my eye during the procedure?

The latest technology for LASIK contains an eye-tracking system that follows your eye’s movement; when your eye moves in one direction or another, the laser will follow precisely. Additionally, the numbing drops and muscle relaxers given before the procedure alleviate much of the eye’s movement. Blinking is not possible since the eyelids are held open with gentle pressure from specially designed eyelid-holder.

Because modern LASIK is computer-driven, this means that human error is greatly reduced. Complications from LASIK surgery are quite rare, and nearly all patients recognize an improvement in vision after their LASIK procedure. Contact the Orlando LASIK specialists at Magruder Laser Vision for a free consultation with our dedicated staff by calling 407-843-5665. Doc Brock and his staff will discuss the LASIK procedure in detail with you and answer any additional questions at that time.

Case of the issue: Scleral Tattoo Gone Wrong

It’s always good to be aware of the latest trends that patients are partaking of in the name of style which may affect their health. This is one which I have only recently been made aware of, and as an Orlando eye surgeon, one that I very much hope does not catch on.

This case comes from Alberta, Canada, where a 24-year-old male presented with severe vision loss after a scleral tattoo procedure. Reportedly, a tattoo artist attempted to inject ink into the subconjunctival space with the goal of dying the sclera. The artist penetrated the globe with the tattoo needle and injected ink into the vitreous cavity after striking the crystalline lens with the needle. This patient, unfortunately, developed endophthalmitis, and despite vitrectomy and intravitreal antibiotics, lost the eye. 

(Clicking on any of the images below will redirect to an excellent short 2-minute video of the case with imaging, surgical video, and pathology slides.)

Figure 5. Green dyed sclera, edematous cornea, and anterior chamber filled with green dye impairing view of iris, lens, and posterior segment.

Figure 6. Surgical photo illustrating chemotic conjunctiva, subconjunctival green dye, injection, anterior chamber filled with dye

Figure 7. After entry incision to anterior chamber was made, green tattoo ink dye rapidly egressed from the eye

A brief google search showed that scleral tattoos, while quite uncommon, have been growing in popularity over the past decade. Oklahoma made performing scleral tattoos a misdemeanor in 2009, but elsewhere it appears that the tattoo artist community believes that their licensure covers performing of this procedure. I am not aware of any legal cases which litigated the matter. Let’s hope this doesn’t catch on in Florida! 

Freund, Paul et al. Scleral Tattoo Gone Wrong. May 2017. Available: https://www.aao.org/clinical-video/scleral-tattoo-gone-wrong

 

 

The Posterior Cornea – What Secrets Does It Hold?

The curvature of the posterior cornea has stolen some of the spotlight from its anterior surface sibling over recent years. Two increasingly important roles the posterior corneal curvature plays in our patients relates to astigmatism correction in cataract surgery and in the surveillance of patients suspicious for keratoconus or forme fruste keratoconus.

Role of posterior corneal curvature in cataract surgery:

Toric intraocular lenses and laser arcuate incisions allow cataract surgeons to treat a patient’s corneal astigmatism at the time of cataract surgery. After the cataract is removed, any lenticular astigmatism is removed along with it, and the remaining astigmatism to be treated belongs only to the cornea. Until relatively recently, all methods of measuring corneal astigmatism focused exclusively on the anterior surface of the cornea. These methods include manual keratometry, Placido disc-based corneal topography, and optical biometry devices used for IOL calculations (e.g. IOL Master and Lenstar).

The posterior surface of the cornea also refracts light at its interface with the aqueous. Until recently,  we didn’t have devices to directly measure posterior corneal topography, so posterior corneal astigmatism could only be derived indirectly after cataract surgery. For example, after the cataract is surgically removed, along with any lenticular astigmatism, assuming the IOL is well-centered and not tilted, the total corneal astigmatism could be related to the astigmatism found on manifest refraction. The posterior corneal astigmatism is then the difference between the manifest astigmatism and the measured anterior corneal astigmatism. Nomograms have been developed based on populations studies of posterior corneal astigmatism which can be incorporated into toric IOL selection, and have improved outcomes compared to lens selection without accounting for the posterior curvature. (1)

While the previously mentioned nomograms have been a significant step forward in surgical astigmatism management, they aren’t perfect. The problem is that they are a “one-size-fits-all” solution to the problem based on mean statistics from population studies. As a result, they may not be suitable for an individual patient. Newer research suggests that making IOL selection adjustments based on the measured posterior corneal astigmatism may achieve better outcomes. (2)

We now have a newer generation of topographers which are able to measure the posterior corneal topography using Scheimpflug imaging or ray tracing technologies. And along with this exciting, new information, a challenge has emerged for surgeons – which is figuring out what to do with it…

Our approach is to use a variety of measurement devices, looking for reliability and consistency between measurements. In our office, we use the Pentacam (Scheimpflug) and Galilei (Dual Scheimpflug and Placido based) corneal topographers, and the iTrace ray-tracing wavefront aberrometer and topographer, in addition to the IOL Master. We’ve found excellent outcomes in patients with consistent and high-quality data across a variety of measurement platforms, applying validated nomograms where appropriate, but adjusting for outliers in the measurements of the individual patient.

Case example illustrating the value of incorporating posterior corneal measurements in cataract surgery:

48 year-old gentleman with vague history of blunt trauma to the right periorbital area and a cataract on that side. Best corrected VA OD = 20/60. His corneal topography from the Pentacam is in Figure 1:

Figure 1. Pentacam scan illustrating the patient’s anterior and posterior corneal astigmatism

Surgical decision making:

This patient has a whopping 0.8 D of against-the-rule posterior corneal astigmatism as measured by the Pentacam. This makes him quite the outlier. Consider Figure 2 below, which shows a scatter plot from a study of the magnitude of posterior corneal cylinder power relative to anterior surface cylinder power. Of the 364 eyes measured in this study, only 4 had posterior corneal astigmatism greater than 0.8 D. (3)

Figure 2. Magnitude of anterior corneal astigmatism versus posterior corneal astigmatism for patients with anterior corneal with-the-rule astigmatism

If we decided to treat our patient based only on the anterior corneal astigmatism from the Pentacam measurement, the patient would be left post-operatively with 0.8 D of against-the rule astigmatism. Twice as much astigmatism as he had pre-operatively. Not ideal. (See Figure 3)

Figure 3. Illustration of resultant post-operative astigmatism, if only the anterior corneal astigmatism is treated.

If we combine the patient’s anterior and posterior astigmatism, using a process called vector summation, we calculate the following resultant amount of corneal astigmatism (shown in Figure 4):

Figure 4. Illustration of resultant vector summation of our patient’s anterior and posterior corneal astigmatism

At this point, we compare data from our other measuring devices with the Pentacam data displayed above. Fortunately, in this case, the patient’s measurements were all quite consistent between devices, increasing our confidence in our surgical treatment plan, and resulting in outstanding post-op uncorrected vision for our patient. In this case, the key to our patient’s excellent surgical outcome was factoring in his posterior corneal astigmatism to the treatment plan.

Next issue we’ll discuss the posterior cornea’s role in the surveillance of patients suspicious for keratoconus. 

(1) Koch, D, et al. Correcting astigmatism with toric intraocular lenses: Effect of posterior corneal astigmatism. J Cataract Refract Surg 2013; 39:1803–1809 (2) Reitblat, O, et al. Effect of posterior corneal astigmatism on power calculations and alignment of toric intraocular lenses: Comparison of methodologies. J Cataract Refract Surg 2016; 42:217–225 (3) Koch, D, et al. Contribution of posterior corneal astigmatism to total corneal astigmatism. J Cataract Refract Surg 2012; 38: 2080-2087